Tires: Rotating weight vs radial construction

[Bobby Fazio]

Would you rather run a 30lb radial or a 20lb bias ply? My problem is no one makes a drag radial less than 30" and I can't fit a 30" tire under my 5.0. I am either forced to use a heavier 275/60/15 street radial tire with a questionable tread width of 8.5-9.5" or use a lightweight bias ply 28x9 slick. Are radials worth as much ET as everyone says?

Does NHRA have a ruling on 275/60/15 in stock eliminator? I would really like to use the new Goodyear 4305 but different websites advertise different tread width for it. Neither the Hoosier or Goodyear trucks had any DOT radials at zmax so we couldn't measure.

[Eric Merryfield]

Originally Posted by SStock1373

Would you rather run a 30lb radial or a 20lb bias ply? My problem is no one makes a drag radial less than 30" and I can't fit a 30" tire under my 5.0. I am either forced to use a heavier 275/60/15 street radial tire with a questionable tread width of 8.5-9.5" or use a lightweight bias ply 28x9 slick. Are radials worth as much ET as everyone says?

Does NHRA have a ruling on 275/60/15 in stock eliminator? I would really like to use the new Goodyear 4305 but different websites advertise different tread width for it. Neither the Hoosier or Goodyear trucks had any DOT radials at zmax so we couldn't measure.

Bobby try the hoosier dot radial they are really lightweight for a DOT tire..24lbs which is close to the weight of a 30 inch drag radial..but you will have to do with the 28 inch diameter

If you can fit a 295-65-15 you will get 29.6 od, for 27 pounds..The MT et drag radials are the 38 pounders, but they are a very stout tire, were/are the choice for the super fast outlaw type cars, but they are 30 inch tires.

I think the critical question for you is are you going to running a stick? If so the radial might work or not, with a low HP pure stock style Stang.

On a non tire question......how do you block just the middle bulb?

Eric

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[Bobby Fazio]

Eric, the hoosier dot radial was my other choice but it is a 10" tread width according to their website and jegs/summit sites so I don't know if its legal in stock eliminator. I am using an 8" rim so I don't know if that would bring it down to legal tread width.

[Chris Hill]

Gut says lower rolling resistance of radial will be faster than lower rotational inertia of bias ply tire.

Rotational inertia is more a factor the faster it spins and axle/tire wheel combo is very low speed relatively speaking. Axle rpm though traps will be in 1,500 rpm range for a stocker.

Figure the stick guys would chime in here. Similar to a heavy vs. light flywheel debate and I don't have a dog in that fight.

[tj310]

Rotating weight is not the same as flywheel weight . A heavy flywheel may help launch. Heavier rotating weight ( wheels tires brakes axles ) is just extra weight to accelerate. Depending on who's formula you believe tire weight is about 3 times as important as dead weight. ---Trevor

[Todd Geisler]

You need to find out if a 275/60 D/R is legal for Stock or not.

If so, the Hoosier is a very good choice. For the past couple years it has been the tire of choice for X275 racers running as quick as 4.70's in the 1/8 mile with 60's in the mid teen range, so it's a proven performer. The Hoosier weighs 24 lbs each.

Mickey Thompson came out with a tire to compete with the Hoosier which it's new part number is 3754X. Not fully released right now and again, need to verify legality for the stock class. The new M/T weighs 32 lbs each.

Rumor has it Hoosier wasn't happy with M/T coming out with it's new "Pro" 275 and is planning a tire to compete with it. Should be interesting to see if and how this plays out.

If legal, put them on a 10" rim.

[Ed Wright]

Originally Posted by Eric Merryfield

On a non tire question......how do you block just the middle bulb?

Eric

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Eric, I bought some thin, clear Lexan from Ace Hardware to make mine. One for each lane. Cut with the other side of the tree blocked, and a notch for my lane. Painted flat black from the stage lights down. Doesn't take a very wide strip to block two ambers from that distance. Narrower than a strip of electricial tape. Could just as easily just block the second amber.
Without moving my head around I can see both lanes stage, then nothing else until my third amber. If I could see my first amber, I would be red every time.

I had aluminum blinders before, which required getting my head in position after staging.
Since I pretty much always leave first, if the starter is fast my side of the tree sometimes started down by the time I got my head positioned. I'm old, so am kinda slow. With these

I see everything I want to see without moving around.

When I A-B-A tested same size (9" at the time) radials versus bias tires on my car, the radials were a solid 2/10ths and nearly three MPH. I had just started trying to race again. Not sure it was a bright thing to do. Anyway, Pete Peery told me they would be worth over a tenth. I kinda doubted it, he hasn't steered me wrong yet. They were the same size, same brand (Hoosier at the time) on identical wheels. All passes within an hour.
Had to adjust my lights. Started going red with the radials.

You mentioned tire weight. I have a pair of MT radials on the car. Also, on identical wheels, a pair of same size within 1/4" roll out Goodyears. They are 5 lbs per tire heavier than the MTs.
They hook just as hard, my lights are the same, but they are 4 hundredths slower at the 1/4 mile, 2 hundredths in 60'. Must be the effect of inertia due to the weight, right? Five lbs on a 31" radius has a bigger effect tha five lbs off a 15" wheel, or a crank shaft. Wouldn't that be right?

[ALMACK]

Ed:
So the Goodyear rears have a total of 10 lbs more rotational weight and slowed the car .04 sec. ?

Good info there.

Since I have a 4 cyl. car I am looking at going to a shorter tire and a taller gear in the lighter classes I run. I'll keep the 4.56 rear and 30" slicks for the heavier classes.
I am hoping to reduce my rotational weight. Every little .01 counts.

[Ed Wright]

Yes sir. I would think it would slow a faster car less, probably effect a slower car more?
I haven't owned a set of Hoosiers this size (13"x31") so don't know what they weigh.
I have found taller makes more difference than wider as far as hooking also. May not be the same for other cars or tires. Has been the case with everything I have had.

Edit: I would think the tire weight ET effect would also lessen with smaller diameter tires? Like 28" instead of my 31"?
You can tell I'm just an old Okie, not an engineer.

[ALMACK]

Well, I have ran enough passes on some M&H DOT Drag radials in the last 8 months to come to a conclusion.
The DRs runs the same as my Hoosier 30 inch tall slicks on my car, even tho the drag radials are considerably heavier.( my car runs mid 12's)

Right now, I am running 28 inch tall M&H dot drag radials that I bought in 2007 mounted on 17 x 8 wheels.

They hook just as good and run the same e.t. numbers as my Hoosier 30 inch slicks on 15 x 8 wheels.

So now I need to find out if NHRA will allow 275-60-15 DOT Drag Radials from M/T in Stock.
My old M&H tires will soon wear out and my slicks are used up.